libfluidsynth1 depends on libjack

These are built on a Ubuntu-18.04 (bionic) and I'm currently testing the
AppImage on a Fedora-28 system.
Our AppImage includes libfluidsynth1 as hard Beast dependency, but that in turn
depens on libjack-jackd2-0 which is *not* included in the AppImage. The reason
libjack.so.0.1.0 is not included is that it's blacklisted by the AppImage tools,
because it tends to be tightly coupled to jackd:

Re: libfluidsynth1 depends on libjack

Hi!

On Fri, Sep 28, 2018 at 11:30:01PM +0200, Tim Janik wrote:

> Our AppImage includes libfluidsynth1 as hard Beast dependency, but that in turn
> depens on libjack-jackd2-0 which is *not* included in the AppImage. The reason
> libjack.so.0.1.0 is not included is that it's blacklisted by the AppImage tools,
> because it tends to be tightly coupled to jackd:
>
> https://github.com/AppImage/AppImages/blob/master/excludelist>
> So basically, because of Beast depending on libfluidsynth.so.1, and that
> depending on libjack.so.0.1.0, Beast cannot be run on Fedora eventhough it does
> not *USE* libjack.so.0.1.0:
>
> $ ./beast-0.13.0-alpha-341-g36a856c.x64.AppImage
> ./beast-0.13.0-alpha-341-g36a856c.x64.AppImage: error while loading shared
> libraries: libjack.so.0: cannot open shared object file: No such file or directory
>
> Can you look into whether it's feasible for us to build a libfluidsynth version
> (on bionic) that's good enough to fulfill the requirements of libbse, but not
> link against libjack?

It is relatively simple. Fluidsynth is switching to cmake, automake is
deprecated, so here is a shell script that will build fluidsynth using cmake
without all kinds of stuff we don't need anyway.